Dispersible moist wipes are generally intended to be used and then flushed down a toilet. Accordingly, it is desirable for such flushable moist wipes to have an in-use strength sufficient to withstand a user's extraction of the wipe from a dispenser and the user's wiping activity, but then relatively quickly lose strength in household and municipal sanitization systems, such as sewer or septic systems. Flushable moist wipes must be compatible with home plumbing fixtures and drain lines, as well with onsite and municipal wastewater treatment systems.
One challenge for some known flushable moist wipes is that it takes a relatively long time for them to lose strength in a sanitation system as compared to conventional, dry toilet tissue thereby creating a risk of decreased compatibility with wastewater conveyance and treatment systems. Dry toilet tissue typically exhibits lower post-use strength fairly quickly upon exposure to tap water, whereas some flushable moist wipes may require a relatively long period of time and/or significant agitation within tap water for their post-use strength to decrease sufficiently to allow them to disperse. Attempts to address this issue (i.e., attempts to make the wipes lose strength more quickly in tap water) often reduce the in-use strength of the flushable moist wipes below a minimum level deemed acceptable by users.
Some known flushable moist wipes are formed, at least in part, by entangling fibers in a nonwoven web. A nonwoven web is a structure of individual fibers that are interlaid to form a matrix, but not in an identifiable repeating manner. While the entangled fibers themselves may disperse relatively quickly, some known wipes require additional structure to improve in-use strength. For example, some known wipes use a net having fibers entangled therewith. The net provides additional cohesion to the entangled fibers for increased in-use strength. However, such nets do not optimally disperse.
Some known moist wipes obtain increased in-use strength by entangling bi-component fibers in the nonwoven web. After entanglement, the bi-component fibers are thermoplastically bonded together to increase in-use strength. However, the thermoplastically bonded fibers may negatively impact the ability of the moist wipe to loss strength in a sanitization system (e.g., tap water) in a timely fashion. That is, the bi-component fibers and thus the moist wipe containing the bi-component fibers may not readily loss strength when flushed down a toilet.
Other known flushable moist wipes add a triggerable salt-sensitive binder. The binder attaches to the cellulose fibers of the wipes in a formulation containing a salt solution, yielding a relatively high in-use strength. When the used moist wipes are exposed to the water of the toilet and/or sewer system, the binder swells thereby allowing and potentially even assisting in the wipes falling apart, which allows for relatively rapid strength loss of the wipes. However, such binders are relatively costly.
Still other known flushable moist wipes incorporate a relatively high quantity of regenerated natural fibers and/or synthetic fibers to increase the in-use strength. However, the ability of such wipes to disperse in a timely fashion is correspondingly reduced. In addition, the higher cost of regenerated natural fibers and synthetic fibers relative to natural fibers causes a corresponding increase in cost of such known moist wipes.
Thus, there is a need to provide a wet wipe made from a dispersible nonwoven web (and a method of making such a web) that provides an in-use strength (e.g., wet CD tensile strength, wet MD tensile strength, burst strength) expected by consumers, loses strength sufficiently quickly, and is cost-effective to produce.